Unique MMS problem!

[svtvagabond]

I'm having trouble sending MMS messages on my iPhone 3g. I have 5.0 loaded in and I currently have the general messaging plan on my account by putting my SIM card in a Nokia 2910 GoPhone.

Here's the weird part: I don't have the camera button unless I have some sort of settings typed in under MMS in the Cellular Data menu. I haven't heard of anyone else having this problem.
No matter what info I put in there, I still cannot send a message. By all accounts I should leave this blank, correct? (except for APN - wap.cingular)

Other issues: when I have the SIM card in the Nokia, I cannot access MediaNet from the phone. But it will allow me on the site when I'm using the Nokia. Help?

[IvanPK]

Ya, the MMS button seems to go away and come back with certain settings. Give ATT a call and ask them to remove the MMS Opt-Out Code, and make sure that they have Added or you currently have the General Messaging Plan - sticking your SIM in the Nokia won't change this for you, you have to call.

[svtvagabond]

I've got a guy on the line, but he says I do not have any Opt-Out code on my account right now.
Certainly on the General Messaging plan, 2 operators have verified that for me.